The well-known high affinity reaction between biotin and streptavidin or avidin is a versatile tool in biomedicine. However, any substrate carrying streptavidin or avidin on its surface is trombogenic in contact with blood. Surfaces comprising streptavidin or avidin can also trigger other unwanted reactions in contact with other biological media. Therefore, such substrates are not suitable for applications intended to be in contact with blood or other biological media. Efforts on developing e.g. blood compatible surfaces have previously been described in the literature, with various results. However, so far no fully satisfactory means and methods have been devised.